The present invention relates to a molded wood composite article particularly useful as a door skin or door-facing surface, and to a method of making the molded wood composite article, preferably having an inclined profile embossed or molded into a depression-interior portion of the article. More particularly, the molded wood composite article of the present invention is made from a combination of cellulosic fibers, and a natural or synthetic binder, such as a phenol formaldehyde or urea formaldehyde resin, including at least about 80% cellulosic material, and molded from a mat having at least an upper surface formed from refined, fibrillated cellulosic fibers, e.g., a fiberboard mat, such as that hot-pressed to produce hardboard. The upper surface of the molded article, including any inclined depression-interior surfaces, includes a finely textured hardwood grain pattern, such as oak, containing closely spaced embossed ticks, simulating furniture grade natural wood. The major surfaces of the articles are molded from a planar layer or mat of cellulosic material, e.g., a fiberboard mat, made either by the wet process or the dry process, preferably the dry process. The embossed grain pattern covers an entire outer major surface of the composite article, including, when present, the depression-interior inclined molded profile, and does not blister, has relatively constant paint holdout, and provides excellent embossing fidelity, while providing a closely spaced, finely textured wood grain pattern, with planar outer surfaces disposed between embossed ticks that form the grain pattern.
Man-made boards, such as fiberboard, e.g., hardboard, commonly are embossed on their intended visible major outer surface in the manufacture of interior paneling, exterior siding, and particularly in the manufacture of door skins that are laminated to a support structure or frame, on both major surfaces, for replicating single-panel or multi-panel doors having surfaces that are man made, rather than the very expensive natural wood doors. Commonly, such articles are molded from a planar, loose cellulosic mat to include one or more interior or xe2x80x9cclosedxe2x80x9d depressions, within an interior of the article, such as one or more square or rectangular depressions that do not extend to an outer edge of the article.
The cellulosic fibers used to form the loose mat, e.g., a 1xc2xd or 2 inch thick layer of cellulosic fibers having a specific gravity of, for example, 0.6, initially may be bone dry after the fibers have been dried and felted, but the cellulosic fibers in such mats absorb moisture from the atmosphere and generally include about 2% to about 10% moisture when molded via hot pressing, depending upon the humidity in the region where such mats are stored and/or manufactured.
Natural wood grain patterns have been replicated in fiberboard surfaces by transferring a photographic image of the grain pattern into an embossing plate, by an etching process, to form raised portions or elongated spikes in the surface of the embossing plate and then pressing a loose fiberboard mat with the embossing plate to provide bundles of natural wood ticks that form the grain pattern on the resulting fiberboard surface, as well known in the art. A wood grain pattern is a cluster or bundle of spaced xe2x80x9cticksxe2x80x9d that extend in a pattern, similar to the pattern shown in FIG. 1. The wood grain replication process is successful so long as the grain pattern that is replicated is a relatively loose grain pattern, where adjacent xe2x80x9cticksxe2x80x9d (relatively short, relatively thin embossed depressions that form a bundle or cluster, and the bundle or cluster of ticks is arranged in a pattern of lines to form the wood grain pattern) are sufficiently spaced so that adjacent tick replicating spikes on the embossing plate, which emboss adjacent ticks in a bundle to form the replicated grain pattern into the fiberboard surface (as shown in FIG. 3), do not also depress the planar surface of the fiberboard disposed between adjacent ticks of a bundle (see FIG. 4).
Attempts to replicate tight grain patterns, present in slower growing hardwood trees having bundles of ticks with very closely spaced adjacent ticks, has not been successful since such close spacing of protrusions or spikes from the surface of an embossing plate will depress intended planar areas disposed between closely spaced, adjacent ticks, together with the tick area, as shown in FIG. 4. While it may be possible to replicate a tight grain pattern in the surface by embossing closely spaced ticks into a fiberboard mat formed from highly refined cellulosic material, the degree of refining would be cost prohibitive on a commercial scale.
Additional problems occur in attempting to form inclined molded portions on an interior surface of closed depressions in a molded wood composite article, particularly when it is commercially necessary to paint such inclined surfaces to provide an aesthetically pleasing tight wood grain pattern in the outer surface. One type of product, in particular, that must include excellent embossing detail and superior aesthetic qualities to be commercially acceptable, is a door skin that simulates a single-panel or multi-panel natural wood door on both major faces of a support substrate or frame member. Door skins, or door faces, require detailed, inclined interior molded walls having a plurality of relatively close contours that include varied curved and/or planar surfaces.
It has been found that these interior, inclined molded surfaces of interior inclined molded depression walls are very difficult to provide with a tight wood grain pattern of ticks and to paint uniformly due to density differences, because of various adjacent curved and/or planar contours and due to the confined locations of the inclined surfaces within the relatively small, molded depressions. These angled or inclined surfaces on wall portions molded into depressions formed in the interior of the product are extremely difficult to provide with embossed surfaces representing a tight wood grain pattern, since such embossed texture on depression-interior inclined walls have a tendency to cause the article to stick to the mold cavity at the embossed inclined wall, causing fiber to pull away from the surface of the molded article when it is removed from the mold cavity.
The molded wood composite articles of the present invention solve some or all of the above-mentioned deficiencies in prior art molded wood composite articles to provide a molded wood composite article that includes a tight grained hardwood pattern having excellent embossing fidelity that can be painted with uniform paint hold-out; can include, in the preferred embodiment, molded, inclined surfaces that are accessible for buffability, and wherein the planar upper surfaces, as well as the molded, inclined depression-interior surfaces, are capable of being embossed with excellent texture and tight grain detail to provide an extremely aesthetic, detailed texture or wood grain design.
xe2x80x9cTick spacingxe2x80x9d is measured from centerline to centerline of adjacent ticks through a straight line that most closely approximates a right angle to each centerline.
xe2x80x9cTick bundlexe2x80x9d is a grouping of adjacent ticks that forms a wood grain appearance separated by a tick-free span from an adjacent tick bundle.
In brief, the present invention is directed to a molded wood composite article man-made from wood fibers on at least an upper, molded surface of the article, and a method of manufacturing the article to include a tight, finely textured grain pattern and textured aesthetics on a upper surface, as well as on any depression-interior, inclined surfaces, of the molded articles, while preventing embrittlement, softness and blistering of the article along the depression-interior inclined surfaces.
Accordingly, one aspect of the present invention is to provide molded, wood composite articles and a method of manufacturing the articles, wherein the articles are molded from a loose mat of cellulosic fiber and binder, such that the articles have an embossed, tight wood grain pattern including adjacent, closely spaced embossed ticks with planar surfaces between adjacent ticks.
Another aspect of the present invention is to provide molded, wood composite articles, and a method of manufacturing the articles, that include interior molded depressions having inclined, decorative surfaces that have an aesthetically superior tight wood grain pattern along the entire inclined surfaces, which are not brittle or blistered as a result of the molding process, and such that the articles can have an embossed, tight wood grain pattern on the entire outer surfaces of the article, including adjacent, closely spaced embossed ticks with planar surfaces disposed between adjacent ticks.
Another aspect of the present invention is to provide a molded, wood composite article, and method of manufacturing the article, containing at least about 80% cellulosic material, that is molded from an incompletely consolidated planar mat or preform using heat and pressure to include a decorative wood grain pattern of ticks, wherein adjacent ticks that form part of a tick bundle having three or more adjacent ticks are spaced no closer than 0.016 inch, and adjacent bundles of ticks are spaced by tick-free regions that are at least 0.050 inch and up to 0.280 inch at their widest tick-free span to provide excellent embossing fidelity in a molded, tight wood grain pattern.
The above and other aspects and advantages of the articles and methods of the present invention will become more apparent from the following detailed description of the preferred embodiments, taken in conjunction with the drawings.